This invention relates to fastener installation tools, and in particular to installation tools for installing breakstem fasteners, wherein a part of the fastener is broken off during installation.
Fastener installation tools for breakstem fasteners, such as a blind rivet or bolt, install the fastener by applying a relative pulling action to the stem of the fastener, until the stem is caused to break at a weakened or breakneck point, leaving part of the stem plugging the body of the fastener. The tool may incorporate a pneumatic or hydraulic intensifier, whereby the pulling stroke of the head is actuated when hydraulic fluid enters an inlet port provided in the forging (or casting) of the tool head. Such tools are well known, for example those available under the trade mark Genesis.
The inlet port extends into the tool head from a bore formed in the forging. Currently known tools have inlet ports which are circular in cross-section.
During the broaching of a fastener by the installation tool, the pressure within the head of the tool reaches a peak. This pressure peak consequently causes stresses in the head forging, and particularly around the hydraulic inlet port. The operational life of the head is consequentially limited, as it will eventually fail by cracking around the hydraulic inlet port. The tool is therefore rendered unusable until a replacement head has been fitted.
The value of the pressure peak within the head on broaching increases with the broach load which must be applied to install the fastener, i.e. the force which must be applied to cause the fastener stem to fracture at the breakneck point. As the type and fastening strength of fasteners has improved, the pull forces required to broach fasteners has likewise increased, increasing the stress on forged heads and reducing the life of the tools.
It is an aim of the present invention to overcome or at least mitigate the above problems.